1. Field of the Invention:
The present invention relates to a tool for supporting a composite camshaft having a steel shaft and a sintered piece while the sintered piece is joined to the steel shaft through sintering in a sintering furnace.
2. Description of the Prior Art:
A composite camshaft having a steel shaft and sintered elements, such as a cam, a journal, a gear and a fitting means for a spanner, is well known. Japanese Utility Model Publication No. SHO 51-7367 discloses a composite camshaft of this kind, in which at least a cam and a journal is constructed as a sintered element and is joined to the steel shaft through sintering.
When a sintered piece is joined to a steel camshaft, the sintered piece is first fitted to the steel shaft and then is integrally joined with the steel shaft through diffusion between the sinter and the steel shaft under heating in a sintering furnace. When such sintering is done in a sintering furnace, a tool for supporting a plurality of camshafts to be sintered has been used and usually a plurality of such tools are piled in a vertical direction to make maximum use of the limited space in the furnace.
Such a tool for supporting the composite camshaft to be sintered has been made of steel because of its economical cost. The steel tool used for supporting composite camshafts has generally been composed of a rectangular steel frame having opposed sides containing grooves and the composite camshaft to be sintered is supported by the opposed sides with its steel shaft portion being in direct contact with the steel frame.
However, the conventional tool with a steel frame tends to deform when it is exposed to an environment of high temperatures, such as a temperature of more than 1,100.degree. C. which exists in the furnace. As a result, such a deformation of the steel tool has made it difficult to use the tool repeatedly as well as giving undesirable influences to the quality of the camshaft itself. Such undesirable influences include a bending of the camshaft, a dislocation of the cam and/or the journal to be sintered with respect to the steel shaft in the axial direction of the camshaft, and a degrading of the joining strength and the matrices of the joint between the sintered piece and the steel shaft.